We are deeply saddened to share the news of the unexpected loss of Katja Brückner. Katja was a predoc in the Developmental Biology Unit (Klein Group) from 1994-2000. After leaving EMBL she continued her postdoctoral studies at Harvard Medical School and she was later an Associate Professor at the Department of Cell and Tissue Biology at the University of California San Francisco. Katja was a Howard Hughes Medical Institute Associate, long-term post-doctoral fellow of the European Molecular Biology Organization (EMBO) and Human Frontier Science Program (HFSP), and Special Fellow of the Leukemia & Lymphoma Society (LLS). She was an active, well-known and much-loved member of the EMBL community and her presence will be greatly missed. May she rest in peace.
Katja’s unexpected death has been a terrible shock for all of us and has put us in deep sorrow. It left us in disbelief. Katja always radiated so much energy, creativity, and ideas, such that she seemed rather protected against personal setbacks. Now she left us in the prime of her life, leaving behind her partner Lutz Kockel, and her two wonderful daughters Ava and Zoe.
Katja was a PhD student in my lab at EMBL Heidelberg from 1994-1999. She joined my lab approximately one year after its establishment and encountered an environment that was rich in ideas and vision, but poor in established methods and assays. She also had to deal with a PhD supervisor who had little experience in mentoring people. Hence, we both had to learn our parts in the game, as we were moving forward. I also learnt a lot from Katja, for example, to trust your own abilities when taking on challenging questions and to persevere when things get tough.
We had just started working on the families of transmembrane ephrin ligands and their Eph receptors and had made some rather intriguing observations suggestive of ephrins modulating the signaling output in our assay system in a way that was independent of Eph receptor signaling. Katja took on a very risky project that aimed at demonstrating that these transmembrane ligands had reverse signaling potential in the cells that expressed them. Katja worked more or less alone under my supervision, working day and night with incredible passion, struggling at times with the lack of reagents and cellular assays, but she was hesitant to bring in more people into this project. She was convinced that she would eventually succeed. The highly interactive environment during our weekly joint lab meetings of the Klein and Giulio Superti-Furga labs gave her mental support for the pursuit of her project. The only major practical help she received were some essential protein reagents from an outside collaborator, Prof. Elena Pasquale (SBP Institute, San Diego). Katja demonstrated that the cytoplasmic tail of transmembrane ephrins gets phosphorylated on tyrosine residues when ephrins engage their cognate Eph receptors on the surface of opposing cells. This observation was the key finding that led to the concept of bi-directional Eph-ephrin signaling. To date, this concept that was independently discovered by the laboratory of the late Tony Pawson, has been validated in vivo in several systems and different labs. Her first author publication in Science from 1997 (in which she is responsible for all the experimental data) is widely cited.
Katja continued her work on ephrin reverse signaling by performing yeast two-hybrid screens with the aim to identify intracellular proteins that would bind the ephrin cytoplasmic tail. She successfully established this technique in my lab and decided, this time, to recruit several outside collaborators to the project, including Peter Scheiffele from the Cell Biology Unit. Katja and her coworkers demonstrated that ephrins are recruited to membrane lipid rafts where they interact with intracellular proteins containing PDZ domains including the small family of glutamate-receptor-interacting-proteins (GRIP). This study, which was published in Neuron in 1999 (and is also widely cited) extended the concept of ephrin reverse signaling to mechanisms not involving tyrosine phosphorylation and represented an important entry point for my lab into the regulation of synaptic plasticity by the Eph-ephrin system.
After having completed her very successful PhD work in my lab, essentially using cell culture models, Katja decided to change the system and to join Steve Cohen’s fly lab at EMBL for a postdoc before moving on to Norbert Perrimon’s lab at Harvard. More recently, as faculty at UCSF, Katja continued to address fundamental questions in development, physiology and disease, using a combination of Drosophila genetics and complementary cell-based systems.
I have always been very proud of Katja’s success in the EMBL PhD program and during her entire career. Having successfully managed to combine her academic career with her life as a mother of two children, she has been an inspiring role model for many of my female students and postdocs. Despite the long distance between the USA and Munich, we maintained a lively friendship with Katja. She would frequently visit us on private events or join our lab alumni reunions, where she would fascinate us with her newest insights and ideas. Beyond science, Katja loved to do something creative and funny, often recruiting others to participate in a group project. Her latest and brilliant artwork that she created together with 17 other lab alumni, decorates my office, and is a daily reminder of what a wonderful friend she has been. We miss her badly.
Katja joined my lab at EMBL for a short stint as a postdoc, after finishing her PhD with Rüdiger Klein. She wanted to learn a bit about fruit flies before going on to her postdoc. Katja was bright, energetic and ambitious – like many of her fellow EMBL students – but I had a particular fondness for her because of her fearlessness and her obvious delight in new challenges. Although she wasn’t in the lab for very long, Katja made an important contribution to understanding Notch-mediated signal transduction by showing that Fringe was a glycosyltransferase enzyme that covalently modified Notch protein and altered its signalling activity. Katja made our lab a more fun and interesting place in a lot of ways – though good humour, banter and enthusiasm for science and life.
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